1. Field of the Invention
The present invention relates to an image display system which uses a fixed-pixel display device, particularly a projector, and to an image processing system adapted to an image display system.
2. Description of the Related Art
Some display devices are capable of displaying various images of different resolution; such display devices include projectors having liquid crystal panels or DMD (Digital Micromirror Devices, trademark of Texas Instruments Inc.), liquid crystal display devices having liquid crystal panels, plasma display devices having plasma display panels (PDP), and EL display devices having electroluminescent (EL) panels. For this reason, in instances where the resolution of an input image represented by an input image signal differs from the native resolution of a liquid crystal panel or other fixed-pixel display device being used, the image data contained in the input image signal (hereinafter also termed “input image data”) is subjected to a resolution conversion process to convert the resolution of the image represented by the image data presented to the fixed-pixel display device (hereinafter also termed “image data for display”) to the native resolution of the fixed-pixel display device. See JP2003-84738A for example.
The resolution of a image represented by image data will herein also be referred to simply as “image signal resolution” or “image data resolution.” The term “resolution” is used herein to denote the number of dots in the horizontal direction (number of pixels) and the number of lines in the vertical direction (number of scan lines) of a image or of a fixed-pixel display device. The number of dots in the horizontal direction is also referred to as the “horizontal resolution” and the number of lines in the vertical direction as the “vertical resolution.”
In conventional image display devices, resolution conversion (hereinafter also termed “display device-specific resolution conversion”) is carried out for the purpose of matching the resolution of input image data to the resolution of the fixed-pixel display device. There are other instances in which a resolution conversion process is used. As in the case of a projector which projects an image onto a screen for example, in instances where the size of the projected image on the screen (also termed “projected size” herein) is adjusted in the projector, it would be conceivable, rather than converting the magnification of the projection lens, to instead utilize a resolution conversion process for the purpose of adjusting the resolution of image data being displayed, to an arbitrary resolution which is different from the resolution of the fixed-pixel display device and which matches the projected size. The use of a resolution conversion process would also be conceivable in cases where only a portion of an input image is to be displayed. Similarly, in other direct-view image display devices, the use of resolution conversion processes would be conceivable in cases where an image is to be displayed at an arbitrary screen size rather than at the full-screen size of the fixed-pixel display device; or where only a portion of an input image is to be displayed. Hereinbelow, resolution conversion for the purpose of converting the resolution of image data for display to an arbitrary resolution or of converting part of an input image to the resolution for an arbitrary window size for a particular native resolution of a fixed-pixel display device will also be referred to as “display size-specific resolution conversion.”
In the case of a conventional image display device, in such instances the input image data would be written to a image memory called a frame memory; and when reading the written data a resolution conversion processor called a scaler would execute the display device-specific resolution conversion process. However, one problem with doing so is that in the resolution conversion processor it is difficult to execute a display size-specific resolution conversion process in addition to a display device-specific resolution conversion process.
For example, consider a case of carrying out a resolution conversion process which involves both a display device-specific resolution conversion process and a display size-specific resolution conversion process, executed in that order. Writing and reading of image data to and from the image memory will be necessary in the display device-specific resolution conversion process; and writing and reading of image data to and from the image memory will also be necessary in the display size-specific resolution conversion process. Thus, the frequency of read/write access to the image memory will entail longer processing times as the amount of image data increases, thus posing the risk of degraded image processing capability.